International Journal of Neonatal Screening Article Long-Term Neurological Outcomes of Adult Patients with Phenylketonuria before and after Newborn Screening in Japan Kenji Yamada 1,* , Seiji Yamaguchi 1, Kazunori Yokoyama 2, Kikumaro Aoki 2 and Takeshi Taketani 1 1 Department of Pediatrics, Shimane University Faculty of Medicine, 89-1 Enya-cho, Izumo, Shimane 693-8501, Japan; [email protected] (S.Y.); [email protected] (T.T.) 2 Secretariat of Special Formula, Aiiku Maternal and Child Health Center, Imperial Gift Foundation Boshi-Aiiku-Kai, 5-6-8 Minami Azabu, Minato-ku, Tokyo 106-8580, Japan; [email protected] (K.Y.); [email protected] (K.A.) * Correspondence: [email protected]; Tel.: +81-853-20-2219; Fax: +81-853-20-2215 Abstract: Japanese newborn screening (NBS) for phenylketonuria (PKU) was initiated in 1977. We surveyed the neurological outcomes of Japanese adult patients with PKU to investigate the long-term effects and of and issues with NBS. Eighty-five patients with PKU aged over 19 years who continued to be treated with a phenylalanine-free amino acid formula were investigated by administering questionnaires regarding clinical characteristics, such as mental ability, education status, and therapeutic condition. Of the 85 subjects, 68 patients were detected by NBS (NBS group), while the other 17 were clinically diagnosed before the initiation of NBS (pre-NBS group). Further, 10 of the 68 NBS patients presented intellectual and/or psychiatric disabilities, 5 of whom had a history of treatment discontinuation; in contrast, 12 of the 17 pre-NBS patients presented with neuropsychiatric symptoms. Regarding social outcomes, almost all patients in the NBS group could live an independent life, while over half of the patients in the pre-NBS group were not employed Citation: Yamada, K.; Yamaguchi, S.; Yokoyama, K.; Aoki, K.; Taketani, T. or lived in nursing-care facilities. Neurological outcomes are obviously improved by NBS in Japan. Long-Term Neurological Outcomes of However, some patients, even those detected by NBS, developed neuropsychiatric symptoms due to Adult Patients with Phenylketonuria treatment disruption. Lifelong and strict management is essential to maintain good neurological and before and after Newborn Screening social prognoses for patients with PKU. in Japan. Int. J. Neonatal Screen. 2021, 7, 21. https://doi.org/10.3390/ Keywords: phenylketonuria; newborn screening; long-term outcome; adult patients; Japanese; ijns7020021 intellectual disability; psychiatric disability; treatment discontinuation Academic Editor: Toshihiro Tajima Received: 3 March 2021 1. Introduction Accepted: 12 April 2021 Published: 14 April 2021 Phenylketonuria (PKU, OMIM No. 261600), an autosomal recessive inherited disease of amino acid metabolism, is a major disease identified by newborn screening (NBS) [1]. Publisher’s Note: MDPI stays neutral Classic PKU is caused by phenylalanine hydroxylase (PAH, OMIM No. 612349) defi- with regard to jurisdictional claims in ciency and is associated with severe intellectual disability, convulsions, hypopigmentation, published maps and institutional affil- behavioral abnormalities, and dementia. Because PKU is detected as an elevation in pheny- iations. lalanine (Phe) levels in NBS, mild hyperphenylalaninemia (HPA), tetrahydrobiopterin (BH4) deficiency, including BH4 metabolic defects, and BH4-responsive PKU and classic PKU are all detectable. Mild HPA is also caused by a defect in PAH but is clinically mild and may require less strict dietary restrictions. BH4-responsive PKU and BH4 deficiency show BH responsiveness. The global prevalence of PKU has been reported to be approxi- Copyright: © 2021 by the authors. 4 Licensee MDPI, Basel, Switzerland. mately 1 in 4000 to 15,000 births [1–3], but the incidence of NBS in Japan has been reported This article is an open access article to be 1 in 50,000 to 70,000 births [4,5]. distributed under the terms and NBS for PKU first spread from the mid to late 1960s in North America and the United conditions of the Creative Commons Kingdom, while nationwide NBS for PKU was initiated in 1977 in Japan. Almost all cases Attribution (CC BY) license (https:// of PKU are detected by NBS and treated immediately after birth. The treatment is mainly creativecommons.org/licenses/by/ a diet with protein restriction and Phe-free formula and supplementation with BH4 in 4.0/). some cases. With this therapy, the life and neurological prognoses of patients with PKU Int. J. Neonatal Screen. 2021, 7, 21. https://doi.org/10.3390/ijns7020021 https://www.mdpi.com/journal/ijns Int. J. Neonatal Screen. 2021, 7, 21 2 of 10 have been reported to improve, at least in childhood, resulting in a significantly decreased societal economic burden [6,7]. Therefore, PKU is considered one of the best targets for NBS in terms of a cost–benefit analysis. However, even in patients who are initially treated and achieve good metabolic control, reversible (and sometimes irreversible) neuropsychiatric symptoms can develop if this control is lost in later childhood or adulthood [8]. In addition, over time, some patients may manifest subtle intellectual and neuropsychiatric issues even with strict adherence to a low-Phe diet [9–12]. In fact, the long-term outcome of PKU is not necessarily favorable. In this study, we expanded upon our previous studies [5,13,14] and investigated the social and neurological outcomes of adult patients aged over 20 years who were diagnosed with PKU before and after NBS in Japan using a questionnaire administered to attending doctors. 2. Materials and Methods We sent questionnaires to the 33 attending physicians of 85 adult patients with PKU aged over 20 years as of October 2016 (born before 1996) who had continuously required a special formula (including Phe-free comprehensive amino acid powder and low-Phe peptide powder) supplied by the Secretariat of Special Formula, Aiiku Maternal and Child Health Center for dietary therapy. Attending physicians answered the questionnaires based on clinical records. The questionnaire included questions on sex, age, clinical form of PKU, history of treatment interruption and the reason, follow-up department, physical development, neuropsychi- atric disability, educational status, work status, and marital status and allowed for an open-ended description of the patient. Regarding the question on neuropsychiatric disability, attending physicians were able to answer “normal intelligence”, “borderline intellectual disability”, “intellectual disability”, and/or “psychiatric disability”. When “intellectual disability” was selected, patients with an IQ (intelligence quotient) less than 50 or patients living in nursing-care facilities were characterized as having a “moderate-severe intellectual disability”, while those with an IQ of 50–70 or who are able to fend for themselves and patients with bor- derline intellectual disability were characterized as having a “borderline-mild intellectual disability”. Additionally, the details of psychiatric disability were judged based on the open-ended description. Regarding physical development, short stature was defined as a height <160 cm for males and <148 cm for females. Obesity and leanness were defined as BMI >25 and <18.5 kg/m2, respectively. The subjects were divided into the following two groups: (1) the NBS group was defined as patients who underwent NBS, and (2) the pre-NBS group consisted of patients who were born before 1977 (when NBS was initiated) or were born after 1977 but did not receive NBS. Each of the groups was subdivided into age groups of approximately 5 years. The results of the NBS and pre-NBS groups were compared without a statistical analysis because of the small-scale nature of this study. This study was approved by the Institutional Review Board of Shimane University on 13 October 2016 (#20160915-2). 3. Results We received answers from the attending physicians of all 85 adult patients with PKU (response rate of 100%). All participants were alive. Because only one patient had not undergone NBS despite being born in 1979, she was enrolled in the pre-NBS group (and classified into the 39–44-year-old subgroup). Eventually, 68 and 17 patients were placed into the NBS and pre-NBS groups, respectively. As shown in Table1, the NBS group consisted of 34 males and 33 females, while 7 males and 10 females constituted the pre-NBS group. The median age (range) of the NBS and pre-NBS groups was 28.5 years (20.5 to 38.2) and 43.9 years (37.7 to 50.8), respectively. Regarding the clinical form of PKU, almost all patients had classic PKU, but six patients with mild HPA and two patients with BH4- Int. J. Neonatal Screen. 2021, 7, 21 3 of 10 responsive PKU were included in the NBS group. In this study, almost all participants (66 of the 68 patients in the NBS group and 16 of the 17 patients in the pre-NBS group) were managed by pediatricians even after reaching adulthood. Table 1. Overview of the participating patients with phenylketonuria (PKU). NBS Group (n = 68) Pre-NBS Group (n = 17) Sex male 34 7 female 33 10 unknown 1 0 Median age (range) [years] 28.5 (20.5–38.2) 43.9 (37.7–50.8) 20–24 22 0 25–29 19 0 30–34 14 0 35–39 13 3 40–44 0 7 45–49 0 6 50- 0 1 Clinical form classic 54 16 mild HPA 6 0 BH4-responsive 2 0 BH4 defect 0 0 unknown 6 1 Follow-up department pediatrics 66 16 internal medicine 1 1 gynecology 1 0 treatment interruption 21 5 HPA, hyperphenylalaninemia; BH4, tetrahydrobiopterin. Approximately 30% of patients (21 of the 68 patients in the NBS group and 5 of the 17 patients in the pre-NBS group) had ever discontinued treatment. Although the description of treatment discontinuation was unequal due to the open-ended questionnaire, concrete information was obtained for only eight patients in the NBS group. Among them, the median age at treatment discontinuation was 18 years (range, 11 to 20 years), and the median duration was 11 years (range, a few years to 23 years).